It is desirable for a refrigeration fluid being delivered from an expansion device to an evaporator coil of a space conditioning system to have a tightly controlled uniform pressure drop throughout the evaporator coil's circuit. For instance, if the pressure drop is not uniform, then the distribution of refrigeration fluid is not the same throughout the coil, and this, in turn, reduces the heat transfer efficiency of the coil. To facilitate a uniform flow distribution of the refrigeration fluid to the evaporator coil, a distributor unit is connected to the output of the expansion device and to different parts of the evaporator coil.
Additionally, space conditioning systems are often designed to accommodate different sizes of evaporator coils, in which case, it is necessary to change the expansion device so as to maintain the desired specific uniform pressure drop. As such, the distributor and expansion device are designed to be detachably coupled together. Typically, the expansion device itself can be reversibly disconnected from the distributor (e.g., through threaded connections) so that an orifice housing in the expansion device can be substituted with a differently-sized orifice housing and then the expansion device and distributor reconnected.